1. Field of the Invention
This invention relates to a reclosable flexible bag formed of a thermoplastic film material. More specifically, this invention relates to a reclosable flexible bag having fastener profiles attached to the exterior walls of the bag.
2. Description of the Prior Art
Various closure arrangements have been proposed for closing plastic bags. For example, U.S. Pat. No. Re. 28,969 to Nito shows the initial Zip-lock storage bag in which a profile extrusion on one side of the bag mates with a profile extrusion on the other side of the bag to form an interlocking, reclosable closure. The interlocking profiles of this closure are integral with the plastic film of the bag.
U.S. Pat. No. 3,226,787 to Ausnit shows an apparatus for extruding the interlocking profiles during the fabrication of the plastic sheet.
U.S. Pat. No. 4,212,337 to Kamp shows a closure device made from a heat sealable material. The closure is attached to the heat sealable film in a separate step after the manufacture of the film. Heat is transferred through the film to produce melting at the interface of the film and the closure device to attach the closure to the film. This type of attachment is a slow process which cannot be practically performed in line with extrusion and bag making.
Recently, it has been proposed that the interlocking profiles be placed outside the bag so that upon closing, the bag walls are interposed between the profiles. The advantage of placing the interlocking profiles outside the bag is that the contents of the bag can come in contact only with the film and not the profiles. This provides a cleaner seal. In addition, a more reliable leak proof seal may be obtained since the two layers of film at the side seams are attached together directly and do not extend beyond the interlocking profiles.
The manner by which the interlocking profiles are attached to the exterior of the bag walls has also been investigated. Accordingly, it has been proposed to affix the profiles directly to the exterior surface the bag walls, with the interlocking parts of the profiles facing each other. This has the disadvantage in that one of the bag films is sealed across the two arm portions of the female interlocking profile. Upon repeated use, this portion of the film may be stretched severely so as to cause rupture. It has also been proposed to attach the interlocking profiles only at the end, i.e. the side seams of the bag. However, such "free" profiles become poorly guided and may be shifted off the top of the bag when the bag is being closed. It has further been proposed to affix the raised portion of the profiles to the exterior walls near the mouth portion of the bag. Thereafter, the walls are folded so as to form a cuff surrounding the mouth of the bag. Although such an arrangement reduces the "wandering" of the profiles, aligning the profiles becomes difficult because of the presence of the cuff and the thin bag film.
The present invention overcomes the above described disadvantages associated with previously known reclosable bag structures.